Brick with wear indicator

ABSTRACT

A ball mill has a lining of bricks with colored inserts extending toward the face of the brick from the back thereof for a distance of one-eighth to one-third the thickness of the brick. When the bricks wear to the point of possibly failing, the colored inserts are readily visible to show that the linear requires replacement. Preferably the colored inserts are of the same refractory material as the bricks themselves and have a coloring material added thereto. This minimizes contamination of the material being ball milled.

United States Patent Inventor Robert F. Rea

Bloomfield Township, Oakland County, Mich. Appl. No. 533,033 Filed Mar.9, 1966 Patented Apr. 13, 1971 Assignee Champion Spark Plug CompanyToledo, Ohio BRICK WITH WEAR INDICATOR 3 Claims, 5 Drawing Figs.

US. Cl. 52/105, 52/596, 52/612, 264/30, 264/60, 106/55, 106/65 Int. Cl.E04b l/l2 Field of Search 264/29, 30, 60; 52/612, 105, 596; 106/55, 58,59, 60; 110/99, 1 l

References Cited UNITED STATES PATENTS 1,198,940 9/1916 McGiehan 52/5961,775,396 9/1930 Jackman et a1. 52/596 2,140,197 12/1938 Batcheller52/612 Primary Examiner-Donald J. Arnold Attorney0wen and Owen ABSTRACT:A ball mill has a lining of bricks with colored inserts extending towardthe face of the brick from the back thereof for a distance of one-eighthto one-third the thickness of the brick. When the bricks wear to thepoint of possibly failing, the colored inserts are readily visible toshow that the linear requires replacement. Preferably the coloredinserts are of the same refractory material as the bricks themselves andhave a coloring material added thereto. This minimizes contamination ofthe material being ball milled.

PAT-ENTEuAPmmn 3,574,269

INVENTOR. .RQBBRT I'HEA bmcw BRICK WITH WEAR INDICATOR This inventionrelates to a brick having means to indicate I when a predeterminedamount of wear of the brick has occurred, and to a method of making sucha brick.

A brick according to the invention is particularly useful in the linerof a ball mill container wherein the liner is subjected to wear whilethe ball mill is operated. In a ball mill, the rate of wear of the lineris difficult to determine and can vary greatly according to such factorsas the type and amount of the charge and the percent of solids therein,the size, density, hardness, and quantity of mill balls, and the rate ofrevolution of the ball-mill container. It is also difficult to determinethe amount of wear, as by measuring the interior of the ball-millcontainer, because the wear varies considerably for different portionsof the container. Such measurements are also difficult to obtain becausemore than half of the volume of the mill container is normally filledwith mill balls. An accurate measurement, consequently, is only possibleby removing many of the mill balls. This requires considerable labor andtime, particularly in larger mills which may contain several tons of themill balls. Consequently, it is easy for the liner to wear, before beingnoticed, to the extent that portions break away and contaminate thecharge. The wear also may be enough that the outer wall of the containeris exposed and worn by the mill balls to the point of contaminating thecharge or even causing failure of the wall eventually.

The present invention relates to a ball-mill liner having marking brickswith indicators or inserts which, when exposed, indicate to the operatorthat the liner has worn a predetermined amount. The marking bricks withthe wear indicators need not be placed throughout the liner but only instrategic locations where wear is greater, or in a predetermined patternin the liner to provide a representation of the wear. Either arrangementkeeps the cost of the liner at a minimum because the marking bricks,which are more expensive, are used only to the extent necessary. Also,the marked or colored insert of each brick is only a small percentage ofthe overall brick. This is important where high purity of the charge isrequired since the contamination from the colored insert will be aminimum.

In a preferred form, the colored insert of the marking brick is of acolored ceramic material, the ceramic material being the same as thatused in the brick, so that a minimum difference in expansion orshrinkage will occur between the brick and the insert and also so thatthe colored material will minimize contamination of the charge, being ofthe same basic material as the brick.

The invention also relates to a method of making a brick with a wearindicator.

It is, therefore, a principal object of the invention to provide a brickwith a wear indicator and a method of making same.

Another object of the invention is to provide a liner for a ball millwhich indicates when a predetermined amount of wear has occurred.

Many other objects and advantages of the invention will be apparent fromthe following detailed description of preferred embodiments thereof,reference being made to the accompanying drawing, in which:

FIG. 1 is a view in perspective, with parts broken away and with partsin section, of a ball mill having a liner embodying the invention;

FIG. 2 is a fragmentary view in perspective of a container of the ballmill ofFIG. 1;

FIG. 3 is a view in perspective of a brick for the liner of the ballmill, which brick has a colored section therein;

FIG. 4 is a view in perspective, with parts broken away and with partsin section, of a slightly modified mill liner brick embodying theinvention; and

FIG. 5 is a view in perspective of a modified brick for the liner of theball mill, which brick has another type of colored section therein.

A ball mill of the general type for which the brick according to theinvention is particularly useful is shown in FIG. 1. The

ball mill basically includes a drive unit 10 for rotating a ball millcontainer 12 which is rotatably mounted on bearing units 14 and 16. Thecontainer 12 has an outer metalwall l8 and a liner 20 and circular endwalls 22 which also can include outer metal walls and an inner ceramicliner similar to the liner 20.

A particularly useful application for the ball mill is in the mixing andgrinding of ceramic batch material for spark plug insulators. Suchinsulators require a high degree of purity as well as a high degree ofuniformity. Consequently, the materials must be mixed for long periodsof time and must be subjected to minimum contamination from the ceramicliner 20. In the event that the liner 20 becomes too thin during use,portions thereof can break away and contaminate the ceramic batchmaterial so as to impair the quality of the final spark plug or otherproduct made with the ceramic material. The wear also can be excessiveto the point that the outer metal wall 18 is exposed with small piecesof metal being worn away and contaminating the batch. Over a period oftime this wear even can cause failure of the outer wall 18 and result inexpensive repairs for the ball mill. The extent of the wear of the liner20 cannot be accurately determined by the length of time the ball millis in use because the wear varies greatly. As pointed out previously,the degree of wear will depend on the type and amount of the charge andpercent of solids, as well as the size, density, hardness, and quantityof the mill balls employed. The rate of revolution of the ball-millcontainer 12 also is afactor in the rate of wear. Attempts have beenmade heretofore to determine the amount of wear of the liner by takingdiametrical measurements in the container 12. This has not been reliableor practical, however, because the wear in the container is not at alluniform and because the measurements are difficult and time consuming toobtain, due to the presence of the mill-balls.

To overcome the above problems, marking bricks 24 are used as part ofthe liner 20. In one form of the invention, the brick '24, as shown inFIG. 3, is of generally rectangular configuration with slightlytaperedsides to fit properly in the cylindrical interior of the wall 18.In a rear surface of the brick 24 is a transverse groove 26 extendingcompletely across the brick and containing a colored marking section orinsert 28. The height of the section 28 should be such that when thesection is exposed after the brick wears sufficiently, the

thickness of the overall brick will still be sufficient that the linerwill not break away and contaminate the batch material being ground andmixed. The height of the section will be from one-eighth to one-thirdthe height of the brick 24 and usually will be from about 1 inch toabout 3 inches thick. The width and length of the colored section 28 arenot critical but these dimensions should be small to minimizecontamination, and yet be clearly visible when exposed. If desired,however, the colored section can constitute a layer extending over theentire back of the brick.

The colored section 28 is preferably made of the same material as thebrick but with a colorant, preferably a strong one, added. By way ofexample, cobalt oxide or chromium oxide are desirable for alumina brick.However, small amounts of oxides of manganese, iron, or nickel, or anycombination, can also be used. Other colorants also can be used but areusually more costly than those just set forth. Examples are titanium,vanadium, and copper compounds. The colored sections can also be made byadding carbon or metals to the ceramic and firing in an inertatmosphere. Amounts of about /2percent to about 2 percent, by weight, ofthe colorants added to the ceramic material are usually sufficient. Bymaking the section 28 of the same material as the brick, the effect ofcontamination is minimized since the contaminating colored material isthe same as that of the brick except for theadditional colorant.

By way of example, the brick and the insert can have the followingcompositions:

Moisture in the amount of 9 percent-12 percent by weight can be added tothe batches and the final shaped brick and insert then fired to cone 16,for example, for vitrification.

The brick 24 of FIG. 3 can be extruded in a continuous body and then cuttransversely to the predetermined brick length. The colored section 28also can be extruded separately and then cut transversely into sectionsequal substantially to the width of the slot 26. The slots 26 are thencut in the larger surface of the brick 24 and the colored sectionscemented in by means of a thick slip made from crushed, raw brick. Theextrusion pressures and other conditions for the brick 24 and thecolored section 28 should be alike and the orientation of the brick 24and the section 28 should be the same to prevent shrinkage cracks whichotherwise can occur, particularly since extruded pieces tend to have ahigh degree of shrinkage. Consequently, if the brick 24 is extrudedlengthwise, then the colored sections 28 should be extruded in widthsequal to the widths of the brick 24 or the length of the slot 26. Theextruded colored section is then cut transversely into sections equal tothe widths of the slots 26.

The bricks 24 need not be used throughout the liner but can be employedonly at strategic positions or in a predetermined pattern as shown inFIG. 2. In this manner, a minimum number of the more expensive markingbrick 24 need be employed and contamination by the exposed coloringsection is a minimum. By way of example, it is sufficient to have lessthan one out of ten of the bricks in the liner 20 be a marking brick.The mill lining wear is usually considered to be about 1 percent of thecharge being milled. Further, if the marking section 28 includes 2percent of the colorant and occupies percent of the area of the brick,the resulting contamination, even if all the colored section 28 wereexposed, would only be 0.0002 percent. As a practical matter, the linerwould be replaced when only a relatively few of all of the coloredmarking sections 28 were exposed.

Another suitable marking brick 30 is shown in FIG. 4. This brick has acylindrical recess 32 in which a cylindrical marking section or insert34 is located. The section 34 can be pressed to shape under apredetermined pressure and then placed centrally in a larger mold cavitywith the uncolored ceramic material pressed around it. By shaping bothpieces at the same pressure, the problem of shrinkage cracks again canbe minimized.

A marking brick 36 of FIG. 5 has a recess 38 in which a marking sectionor insert 40 is located. The brick 36 can be either extruded inaccordance with the method discussed for the brick 24 or can be moldedin accordance with the method discussed for the brick 30. The importantfeature of the brick 36 is that the sides of the insert 40 extendingtoward the face of the brick taper so that more of the colored sectionis exposed as more of the brick wears. In this manner, the amount ofwear can be determined by the width of the exposed colored section. Thethickness of the section 40 may exceed that of the sections 28 and 34but again will not normally exceed approximately one-third the thicknessof the overall brick.

While the section 40 is shown in an elongated shape, it also can be madein the form of a cone or pyramid, if the brick is molded similarly tothe brick 30. The sides of the section 40, rather than tapering towardone another, in a direction toward the face of the brick, can taper inthe opposite direction so that the exposed portion narrows as wearincreases.

Various modifications of the above-described embodiments of theinvention will be apparent to those skilled in the art, and it is to beunderstood that such modifications can be made without departing fromthe scope of the invention, if they are within the spirit and the tenorof the accompanying claims.

I claim:

1. A marking brick for use in a liner of a chamber in which the liner issubject to wear, said brick being of a ceramic material having a recessin the back thereof extending inwardly toward the face a predetermineddistance and terminating short of the face by a substantial distance,said recess being filled with a colored ceramic material which, whenexposed after a substantial portion of said brick wears away, is readilydistinguishable to the eye from the remainder of the brick, said coloredceramic material being from oneeighth to one-third the thickness of saidbrick and of the same size and shape as said recess.

2. A marking brick for use in a liner of a chamber in which the liner issubject to wear, said brick being of a ceramic material having a recessin the back thereof extending inwardly toward the face a predetermineddistance and terminating short of the face by a substantial distance,said recess being filled with a colored ceramic material of the samesize and shape as said recess which, when exposed after a substantialportion of said brick wears away, is readily distinguishable to the eyefrom the remainder of the brick, said colored ceramic material being ofthe same ceramic material as said brick and including a colorant.

3. A marking brick according to claim 2 wherein said colorant consistsof an oxide selected from the group consisting of cobalt, nickel, iron,chromium, and manganese.

1. A marking brick for use in a liner of a chamber in which the liner issubject to wear, said brick being of a ceramic material having a recessin the back thereof extending inwardly toward the face a predetermineddistance and terminating short of the face by a substantial distance,said recess being filled with a colored ceramic material which, whenexposed after a substantial portion of said brick wears away, is readilydistinguishable to the eye from the remainder of the brick, said coloredceramic material being from one-eighth to one-third the thickness ofsaid brick and of the same size and shape as said recess.
 2. A markingbrick for use in a liner of a chamber in which the liner is subject towear, said brick being of a ceramic material having a recess in the backthereof extending inwardly toward the face a predetermined distance andterminating short of the face by a substantial distance, said recessbeing filled with a colored ceramic material of the same size and shapeas said recess which, when exposed after a substantial portion of saidbrick wears away, is readily distinguishable to the eye from theremainder of the brick, said colored ceramic material being of the sameceramic material as said brick and including a colorant.
 3. A markingbrick according to claim 2 wherein said colorant consists of an oxideselected from the group consisting of cobalt, nickel, iron, chromium,and manganese.